This invention relates generally to filtering devices, and more particularly relates to an apparatus for filtering fluid including displacement of a used length of filter medium, and indexing of a new length of filter medium.
In a typical filtration operation, fluid passes through a filter medium, which is located in a filter chamber, in order to strain solid discard particles therefrom. Such filter medium may be sealed in the filter chamber at the ends thereof, in order to prevent fluid bypass for single pass filtration.
In large volume filtration operations, as in direct line tubular filter apparatus, for example, efficiency has been achieved by utilization of continuous lengths of tubular filter media, and means for automatically displacing the tubular filter medium through the filter chamber so as to automatically remove the used length of filter medium and index a new length of filter medium. Furthermore, non-bypass sealing has been provided in such devices by incorporation of seals comprising movable and fixed bearing surfaces which cooperate at the filter medium inlet and discharge sides of the filter chamber.
In displacing the used length of filter medium from the filter chamber through a clearance space between the discharge side movable and fixed bearing surfaces, accumulations of collected discard particles, which become associated with discard particles embedded in the interstices of the filter medium during filtration, interfered with such displacement and adhered to the disharge-side bearing surface with interfered with sealing of the filter chamber. To prevent accumulation of collected discard particles, operational requirements for such apparatus included high fluid inlet pressures, shortened time periods of operation, and limitation of particle sizes filtered to small sized discard particles, thereby substantially reducing the efficiency of operation and the utility and applicability of such apparatus.
In sealing the filter medium in the filter chamber, such seals incorporated large sealing surfaces which required high sealing pressures to operate, limited the internal fluid pressures which the enclosure was capable of withstanding, and were susceptible to seal leaks with resultant fluid bypass.
To remove the used length of filter medium and index a new length of filter medium, filter medium pinching rollers were utilized at the discharge-side end of the filter medium. Discard particles associated with the used length of filter medium being extracted, and solutions used during the filtration cycle, adhered to the rollers, with resultant damage to the roller surfaces and interference with the indexing cycle.